Operation Manual – QoS-QoS ProfileH3C S3100 Series Ethernet Switches Chapter 1 QoS Configuration1-12III. Traffic policingThe typical application of traffic policing is to supervise specific traffic into the networkand limit it to a reasonable range, or to "discipline" the extra traffic. In this way, thenetwork resources and the interests of the operators are protected. For example, youcan limit HTTP packets to be within 50% of the network bandwidth. If the traffic of acertain connection is excess, traffic policing can choose to drop the packets or to resetthe priority of the packets.Traffic policing is widely used in policing the traffic into the network of internet serviceproviders (ISPs). Traffic policing can identify the policed traffic and perform pre-definedpolicing actions based on different evaluation results. These actions include:z Discarding the nonconforming packets.z Forwarding the conforming packets or nonconforming packets.z Marking the conforming packets with 802.1p precedence and then forwarding thepackets.z Marking the conforming packets or nonconforming packets with DSCPprecedence and forwarding the packets.IV. Traffic shapingTraffic shaping is a measure to regulate the output rate of traffic actively. Its typicalapplication is to control local traffic output based on the traffic policing indexes ofdownstream network nodes.The major difference between traffic shaping and traffic policing is that the packets tobe dropped in traffic policing are cached in traffic shaping——usually in buffers orqueues, as shown in Figure 1-6. When there are enough tokens in the token bucket,the cached packets are sent out evenly. Another difference between traffic policing andtraffic shaping is that traffic shaping may increase the delay while traffic policing hardlyincreases the delay.
